Lupus flares when genetically predisposed people encounter certain environmental agents. How the environment alters the immune response to cause flares is unclear. The treatment of lupus is also imperfect, often requiring drugs with significant toxicities. Understanding how the environment causes lupus flares could indicate safer and more effective treatments. The lupus-inducing drugs procainamide and hydralazine, as well as oxidative stress such as that caused by UV light, silica and infections, inhibit T cell DNA methylation and increase expression of genes such as CDI l a , perforin, CD70, CD40L and KIR genes, converting normal